1. Field of the Invention
This invention relates to ball grid array (BGA) packages and more particularly to a method of vent blocking vented BGA packages to provide a cleaner solution barrier.
2. Description of the Related Art
A ball grid array (BGA) package is a type of surface-mount packaging used for integrated circuits (ICs). IC die and other electronic devices are mounted on an interposer substrate and conduct electrical signals through vias in the substrate to an array of solder balls attached to the bottom of the substrate. A lid is sealed to the substrate over the IC die and other electronic devices. A polarity marking such as an ink dot or through-hole is placed towards or at one corner of the package to identify the proper orientation of the package.
The BGA package is placed on a printed wire board (PWB) that carries copper pads in a pattern that matches the solder balls. The assembly is heated in a reflow oven causing the solder balls to melt. Surface tension causes the molten solder to hold the package in alignment with the PWB, at the correct separation distance, while the solder cools and solidifies.
In certain BGA packages vents are formed in the adhesive that seals the lid to the substrate. Venting prevents component pressurization from separating the lid from the substrate while exposed to elevated solder reflow temperatures. However the small vents allow the ingress of potentially corrosive, post-solder reflow aqueous cleaner solution but render rinsing ineffective for removing the cleaner solution. As a consequence, these commercial off-the-shelf (COTS) vented BGA packages are limited to use “no-clean” solder flux and no-clean processes.